There is a system that causes a plurality of virtual machines to operate on a single server device and assigns the virtual machines to terminal devices, respectively, while the terminal devices are connected to the server device through a network. In the system, operating systems (OSs) operate as the virtual machines that operate on the server device. Users operate the terminal devices so that the terminal devices each use the OS of the virtual machine assigned to the terminal device. In other words, the server device is used as a desktop computer for the terminal devices.
A resource such as a central processing unit (CPU) of the server device is assigned to the multiple virtual machines, and the virtual machines operate. The single resource of the server device is assigned to the multiple virtual machines. Thus, the resource may be insufficient depending on an application executed on the OS of the virtual machine when the application causes a high load. In this case, the virtual machines may not operate or a process speed may be reduced. JP2008-293117 discusses a technique for dynamically changing assignments of the resource on the basis of loads of the virtual machines.